Problem: In her language class, Umaima took 5 tests. Her scores were 78, 84, 80, 90, and 88. What was her average score on the tests?
Explanation: The average is the sum of her scores divided by the number of scores. There are 5 scores and their sum is $78 + 84 + 80 + 90 + 88 = 420$ Her average score is $420 \div 5 = 84$.